Method and apparatus for forming subterranean structures

ABSTRACT

A multisection shield incorporates means for subterranean excavation and for conveyance of excavated materials and provides for the installation of the lining planks within the shield. This apparatus is employed in a system of tunnel or conduit lining wherein floor and roof planks are prepositioned and sidewall planks are wedged in place therebetween.

United States Patent [72] Inventor Vernon Cunningham 1,484,188 2/1924 ORourke 61/84 P.O. Box 9337 Springhill Station, South 2,149,345 3/1939 Hunsaker 61/84X Charleston, W. Va. 25303 2,263,352 11/1941 Dow et a1 61/42 [2]] Appl. No. 823,407 3,314,724 4/1967 Tinlin 299/75X [22] Filed May 9,1969 3,404,535 /1968 Tabor.... 6l/85 Patented May 18, 1971 3,404,920 10/1968 Tabor.... 61/85X 3,427,813 2/1969 Hayes 61/85 3,469,884 9/1969 Kampf-Emden 299/75X [54] METHODANDAPPARATUS FOR FORMING FOREIGN PATENTS SUBTERRANEA? STRUCTURES 659,229 3/1963 Canada 299/33 4Cla|ms,8Draw|ng Figs. m E D L T 1 mary xammerenms ay or [52] U.S.C1 299/33,

61/85, 61,45 Attorney Robert G. McMorrow [51] Int. Cl E2ld 23/00 Field of Search 61/85,45, ABSTRACT; A ulti tion hield incorporates means for 3 3 1 subterranean excavation and for conveyance of excavated 56 R f Clad materials and provides for the installation of the lining planks 1 e erences within the shield. This apparatus is employed in a system of UNITED STATES PATENTS tunnel or conduit lining wherein floor and roof planks are 992,813 5/1911 Shepard 61/45 prepositioned and sidewall planks are wedged in place 1,098,961 6/ 1914 Mosher 61/85 therebetween.

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INVENTOR ISAIAH V. CUNNINGHAM ATTORNEY PATENTED-RAY 1 a m SHEET 5 OF 5 INVENTOR IsmAH V. CUNNINGHAM E g-J3 ATTORNEY METHODAND APPARATUS FOR FORMING 'SUBTERRANEAN STRUCTURES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the formation of subterranean tunnels, conduits and other excavations of the type needed illustratively for sewer lines, in mining, and the like. More specifically, the invention comprehends new and novel equipment for safely and speedily forming subterranean openings.

2. Statement of the Prior Art It has heretofore been proposed to employ a shield or encasement with an associated conveyor in the formation of subterranean openings. Such prior devices, often including separable conveyors, digging mechanisms and shields, are shown by way of example in the following US. Pat. Nos. 2,772,871 to Caine issued Dec. 4, 1956; 3,075,591 to Pirrie et al. issued Jan. 29, I963; 3,138,933 to Kemper issued June 30, I964; 3,266,257 to Larrouze et al. issued Aug. 16, 1966; 3,309,142 to Winberg issued Mar. I4, 1967; 3,404,920 to Tabor issued Oct. 8, I968; 3,410,098 to Winberg issued Nov.

SUMMARY OF THE INVENTION This invention relates to that category of tunneling apparatus wherein a shield is forced into the tunneling area, the shield being associated with excavation equipment and conveying means. The present apparatus provides a new and novel means for installation of lining timbers within the shield, and for advance of the shield with respect to the previously installed stand of course thereof, employing said previous stand of course as a base for the advancing mechanism. It is a basic objective of this invention to provide a method and related apparatus for the safe, rapid and economical formation and lining of subterranean tunnels, accomplished through the use of self-contained excavation, conveying and shield means, in which the tunnel lining is prepositioned within the shield. By virtue of the installation of an effective liner within the confines of the shield, there is no section of tunneling exposed to the possibility of cave-ins, dislodgement of large rocks or the like, or other similar mishaps.

A further and related objective of importance accomplished by this invention concerns the provision of a lining system employing planks or timbers which include elongated, substantially rectangular side and base planks, and top planks with slotted corner portions in which the opposite side planks are simultaneously wedged by the application of expansive pressure adjacent the base plank. The apparatus involves elevation means for raising the top planks and for retaining them in elevated location preparatory to installation of the side planks.

This invention comprehends a shield assembly, which, when placed in an initially formed excavation, is thereafter self-advancing as formation of a tunnel progresses. In accomplishing this objective, the shield comprises leading and trailing sections, the leading section having the excavation apparatus, and the trailing section being used as an assembly area for the tunnel lining. Extensible means in the form of a group of spaced apart jacks or the like are positioned medially within the shield and have portions adapted to bear against the lining. Upon extension of these jacks, the shield assembly is advanced with respect thereto, thus providing a space for the positioning of further stands of courses thereof.

By virtue of the employment of spaced apart, individually actuable jack means, the path of movement of the shield is controllable, thereby enabling the operator to maintain a selected course and to readily correct for deviations.

The excavation apparatus hereof, which may take numerous alternative forms and cover various locations, is preferably and ideally located on the roof section of the leading portion of the shield, immediately over a conveyance area. By this means the excavated material is effectively discharged,

' and the space within the shield is conserved.

The present invention, useful in the formation of any type of underground opening, such as a tunnel, conduit, or the like, is adaptable for use in the formation of an initial opening which is later converted, as by the introduction of pipe and grouting to other forms, or alternatively, the opening, employing suitably creosoted or treated timbers, may form a completed subterranean structure usable as a vehicular tunnel, or to form an opening to an underground seam of material to be mined. The invention, in essence, relates to a unique method and apparatus for the formation of said openings.

The shield is formed of heavy material, and is provided with a forward cutting edge aiding in the advance thereof.

Additional objects and advantages of the invention include the incorporation of a self-contained conveyor means for the removal of excavated material from within the shield during operation, and the provision of an inclined leading end plate which effectively transfers material to the conveyor means.

Other and further objects and advantages of the invention will become apparent to those skilled in the art from a consideration of the following specification when read in conjunction with the annexed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view, partially broken away for disclosure of details, of apparatus of this invention employed in the interrelated method of forming a subterranean tunnel;

FIG. 2 is an enlarged transverse sectional view taken on the line 2-2 of FIG. 1, looking in the direction of the arrows;

FIG. 3 is a further sectional view taken on line 3-3 of FIG. 2, looking in the direction of the arrows;

FIG. 4 is a sectional view on line 4-4 of FIG. 3, showing the upper inside portion of the assembly as seen from below;

FIG. 5 is a cross-sectional view on line 5-5 of FIG. 3, showing the lower portion of the assembly;

FIG. 6 is a disassembled perspective view of an elevating apparatus subassembly hereof;

FIG. 7 is an illustration of the manner of placement of side timbers in the practice of the method; and

FIG. 8 is a transverse view in section of a completed tunnel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The environment of employment of the present invention will be understood to be somewhat variable. In some circumstances of use, tunneling excavations are instituted on angular gradients commencing at ground level, while in other circumstances, straight tunneling from a preformed vertical entry bore is desired. In either event, for purposes of description herein, it will be assumed that a section of tunnel has been formed in the ground by whatever means has been dictated by the situation present, and that the apparatus hereof has been assembled and is in place within this preformed tunnel section.

In FIG. 1, the apparatus 20 of this invention is seen in use in the practice of the related method. The apparatus is disposed in the tunnel T in that view, a portion of which has been timbered as will be described below, and a further portion of which is excavated, but not lined. The apparatus is movable forwardly toward the unexcavated area E.

An important and major component of the invention is an enlarged shield 22 formed of heavy metal of the type often employed as annor plating. The shield is here shown in a preferred, rectangular form, but may be polygonal in configuration where tunneling requirements so dictate. As shown in FIGS. 1 and 3, the shield 22 includes a leading section, an intermediate section, and a trailing section. The leading section has a top wall 24, a base wall 26, and sidewalls 28 and 30. The top wall 24 is elongated, and has a leading edge 32 which is extended forwardly of the corresponding front edge 34 of the base wall. An interior reinforcing plate 36 joins the leading edge 32 and declines angularly inward therefrom, having a flange 38 at its connection with the inside of the top wall. In like manner, the sidewalls 28 and 30 have plates 40, 42, respectively, which form sharp leading edges therewith and are inclined from said edges to flanges 44, 46.

At a location spaced inwardly from the leading edges of the walls, a series of channel members collectively identified by reference numeral 48 extend about the inside of the walls and are fixedly secured in place, forming an intermediate brace and support extending about the full interior circumference. The channel members 48 define the interior limits of the leading section of the shield. The top, side and base walls extend over the intermediate section, and terminate at an interior top flange 50, at a base flange 52, and at side flanges 54, 56, respectively. Each of the flanges has a rebent, retaining and reinforcing member 58 thereon.

In FIGS. 3 and a plate system for directing excavated material to a conveyor hereof is shown. An inclined plate 60 extends from the forward edge 34 of the base wall 26 and has a generally triangular form with a rectangular slot 62 formed at its trailing apex portion within the intermediate section. Secured on the plate 60 over the edge 34 is a reinforcing bar 64 with a leading edge 66 which aids in the movement of the shield through the ground. The plate system further includes vertical guide plates 68 and 70 fixed to the side channel mem bers 48 and to the inner edge of the plate 60. The vertical plates terminate at the end of the slot 62, and parallel upstanding plates 72 and 74 extend rearwardly therefrom at that location. Thus, any material which is forced up the plate 60 is discharged through the slot 62 thereof.

The shield assembly 22 further includes a trailing section 72. Like the previously described sections, the section 76 in eludes a top wall 78, base wall 80 and sidewalls 82 and 84. The walls have flanges 86, 88, 90 and 92, respectively. These flanges also have rebent flange sections 94, and the flanges 86, 88, 90 and 92 are respectively fixedly secured to the flanges 50, 52, 54 and 56 of the leading section walls. The respective outer walls are substantially coplanar with one another, and the walls of the trailing section have flat terminal edges uninterrupted by flanges or other protuberanees for a purpose made apparent below.

The apparatus hereof includes new and novel self-contained excavation means. In FIG. 4, it will be noted that the structural members 96 and 98 are extended longitudinally between the flange 50 and the channel member 48 in transversely spaced relation on the top wall 24 in the intermediate section of the shield. A substantially rectangular mounting plate 100 is fixed on the structural members, and has a central swivel plate 102 with curvilinear slots 104, 106 formed therein. These slots receive upstanding connection portions of side-by-side swivel members 108, 110. The members 110 have a fixed extension 112 projecting from one side thereof. A hydraulic cylinder 114 is pivotally connected to the rigidifying member 58 of the top wall, and has an extendable and retractable rod 116 pivotally connected to the extension 112. Suitable fluid supply lines are provided and extend to a control bank or panel 118 shown in FIG. 5. These supply lines, and the control connections therefor, are variable and have therefore been omitted from the drawings for clarity of disclosure. As will be apparent, extension and retraction of the member 116 effects a swivel movement of the members 108, 110 within the limits of the slots 102, 104.

A normally substantially vertical boom 120 is pivotally secured between the members 108, 110 on a pivot pin 122. A second hydraulic cylinder 124 is pivoted between said members at the opposite ends on a pivot 126, and the cylinder has an extensible and retractable rod 128. A pair of enlarged boom plates 130, 132 are fixedly secured to the distal end of the boom 120 on opposite sides thereof, and the rod 128 is pivotally connected between the plates at 132. An elongated arm 136 is pivoted between the boom plates at the ends thereof adjacent the leading shield section, at 138. A third hydraulic cylinder 140 is pivotally mounted between the plates on pivot 142, and its extensible and retractable member 144 is connected between a pair of arm plates 146, 148. A hoe, comprising a flat blade I50 arranged perpendicularly with respect to the longitudinal extent of the arm I36 is fixedly mounted on its outer end, and has rigidifymg or reinforcing gussets of appropriate design. As will be understood from the foregoing, the extension and retraction of rod 128 moves the boom and arm forwardly and rearwardly, and the extension and retraction of rod 144 of cylinder results in generally vertical digging strokes of the hoe. In FIG. 3, it will be noted that downstrokes of the hoe against the material E to be excavated will result in a deposit of loosened material on the inclined plate 60.

To convey the excavated material for discharge on mine cars M or other removal means, the invention provides a conveyance system generally identified by reference 152. The conveyor in this form of the invention includes a frame having sides 154, 156 and a horizontal support plate 158. A series of jacks 160 are secured to the frame sides at appropriate locations and are adjusted such that the frame is inclined upwardly from front-to'rear. The conveyor further includes an endless chain 162 with a series of spaced erossbars 164 which serve to push material placed on the conveyor to its discharge end. The chain is trained about a sprocket on a cross axle 166, mounted on the underside of the plate 60 adjacent to the slot 62 at one end, and at the discharge end of the conveyor about a drive sprocket on an axial 168 driven by a motor 170. The excavated material E is pushed up the plate 60, through the slot 62, and from there onto the conveyor. It is pushed up the conveyor by the crosspieces to the discharge end thereof and into the ear M.

As stated above, it has been assumed for purposes of description herein that an initial tunnel excavation has been accomplished prior to the institution of use of this apparatus and its method of forming and lining a tunnel. As a shield is placed in use, and advanced a measurable distance, for example, about 6 feet, a lining procedure is instituted. This procedure involves initially the laying in place a group of transverse base timbers 172 which rest on the base wall 80 of the trailing section of the shield.

A pair of elevator assemblies 174, best shown in FIG. 6, are employed next in the method. These assemblies 174, which are identical to one another except as to positioning, are each mounted on a vertical channel member 176. One such channel member is secured between the rebent portions 94 of the top and base walls 86, 88 of the trailing section top and base walls, adjacent the opposite sides thereof, whereby an assembly 174 is provided at each side of the shield. Fixed to the channel 176 is an outer channel 178 having a vertical slot 180 extending from substantially its midsection length to its top. A boss 182 is provided at the base end of the outer channel, and a hydraulic cylinder 184 is connected thereto. The cylinder has an extensible and retractable rod 186, and is of course supplied with suitable supply lines leading to the control bank 118. The rod 186 has a clevis 188 on its outer end on which an elongated arm 190 is mounted. The arm 190 has a rectangular block 192 at one end thereof which is dimensioned to be slidable within the outer channel 178, but is too great in size to pass through the slot 180. The arm 190 extends through the slot, whereby upon extension and retraction of the rod 186, the arm is raised and lowered. The control means for the elevation assembly is preferably arranged for simultaneous extension and retraction of each assembly. As a second step in the method hereof, a group of roof or rafter timbers 194, each having slotted lower corners 196 are placed on the arms 190 and elevated into position above the previously placed base timbers 172, as shown in FIG. 3.

With the roof timbers 194 elevated to a position in which they bear against the top wall 78 of the trailing shield section, and the base timbers in place therebetween, side timbers 198, 200 are forced into position. The side timbers are first positioned angularly in opposite pairs, with their upper ends being located in the slotted ends 196 of the roof timbers. A portable hydraulic cylinder 202 with an extensible member 204 is then employed to substantially simultaneously wedge the base ends of the side timbers into place. This frictionally engages the side timbers between the base and roof timbers, and the timbers are, of course, dimensioned for an extremely rigid connection. This procedure is best illustrated in FIG. 7 of the drawing.

The result of completion of the aforesaid process of timber placement results in the formation of tunnel lining or a completed conduit, up to a final course or stand of timbers disposed within the trailing shield section and indicated in the drawing at S. This final course of timbers coacts with the invention apparatus in providing means for advance of the shield. At convenient peripherally spaced positions, a series of push cylinders or jacks 204 are fixed in brackets 206 on the respective walls of the intermediate section of the shield. ln

FIG. 2, it will be observed that these may be, in the rectangular form of the invention herein shown, at the four comers of the device, with a center thrust cylinder positioned on the base. Each of said cylinders has an extensible and retractable rod 208 associated therewith and extended through suitable openings in the abutting flanges of the intermediate and trailing sections of the shield. Each of said rods has an abutment collar 210 which is engageable against the course S. The lining is, of course, immovable due to its manner of formation and also the fact that it is anchored at its terminal by suitable jack means or otherwise. Joint extension of all of the rods 208 therefore results in straight linear movement of the shield forwardly into the earth E. If one or more of the rods is not actuated with the others, the direction of movement is altered, thereby permitting a steering of course alteration of the manner of movement of the shield.

FIG, 8 of the. drawing shows, in a nonlimiting example, one illustrative end use of the system. There, after installation of the timbers according to the invention, a concrete cradle is first poured over the base timbers. A pipe is positioned in the cradle, and a suitable grout fill employed to fill the void space between the pipe and the side and top timbers. Alternatively, if treated timbers are employed, the conduit formed in the practice of the method may be used as is.

lclaim:

1. Apparatus in a system for the excavation and lining of subterranean tunnels, comprising:

I. A substantially rectangular shield having:

a leading section with a base wall, sidewalls and a top wall;

the, top wall having a leading edge projecting forwardly and the base wall having a leading edge;

the sidewalls having inclined leading edges connecting the leading edges of the top and base walls;

an inclined plate mounted above the base wall and having a series of cutting teeth projecting forwardly of the leading edge thereof;

the plate having an elevated discharge end extending inwardly and having side shield members vertically secured thereto;

an intermediate shield section having base, top, and sidewalls common with the leading section, and having a structural member extending thereabout;

the plate extending into the intermediate shield section;

the base, top and sidewalls of the intermediate section terminating at interior, inwardly directed flanges;

a trailing shield section having top, base and sidewalls coplanar with the respective top, base and sidewalls of the leading and intermediate shield sections;

the sidewalls of the trailing shield section having flanges thereon which abut and are fixed to the flanges of the intermediate section;

ll. Excavation apparatus comprising:

a mounting plate secured to the top wall of the inter mediate section; a

a swivel member connected to the mounting plate for limited rotary movement;

a generally vertical boom assembly depending from said swivel member and movable therewith;

first extensible and retractable hydraulic cylinder'means connected to the flange of the top wall of the intermediate shield section and to the boom assembly;

- second extensible and retractable hydraulic cylinder means incorporated in the boom assembly for imparting from front to rear tilt in the assembly about its pivot on the swivel plate;

an arm connected to the boom assembly for vertical pivotal movement, the arm having a cutting blade on its distal end;

third extensible and retractable hydraulic cylinder means mounted between the arm and the boom assembly, whereby the plate is extendable in a cutting stroke forwardly to at least the leading edge of the top, base and sidewalls of the leading shield sections;

III. A conveyor for excavated material comprising:

an elongated conveyor frame having a first end located below said elevated discharge end of the inclined plate; the frame having a second elevated end trailing the shield; support means for the frame; and

an endless, chain-driven conveyor in the frame to convey material disposed thereon from the plate to a remote discharge location;

IV. A liner plank installation means comprising:

a pair of brackets secured in vertical position on the flanges of the sidewalls of thetrailing shield section, each bracket having an upper end and a lower end;

each bracket having a vertically extending slot formed in its upper end and having an attachment adjacent its lower end;

a hydraulic cylinder for each bracket having a stationary portion connected to said attachment and having an extensible rod portion with an exterior clevis thereon;

an elongated support arm in each of said clevises, the support being perpendicularly related to the slide members on one end and having flattop surfaces;

theslide members being slidably disposed in the brackets with the support arms extending through said slots whereby a series of roofing planks placed on the top surfaces are elevated to a position adjacent to the top wall of the trailing shield section;

a lateral hydraulic cylinder portably mounted in the trailing shield section and extensible to a distance such that side planks are forced against the sidewall of the trailing shield section simultaneously; and

V. Shield advance means comprising:

a series of spaced apart hydraulic cylinder assemblies, each including a fixed housing secured to one of the walls of the intermediate shield section and extensible rod member extended through openings formed in the abutting flanges of the intermediate and trailing shield sections; and

the rod members having outer end sections engageable against the planks whereby extension of the rod forces the shield forwardly.

2. Apparatus in a system for the excavation and lining of subterranean tunnels, comprising:

a polygonal shield including a leading section having base, side, and top walls, at least the base and top walls having leading edges;

an inclined plate mounted above the base and having a remote discharge end;

an intermediate shield section of polygonal form corresponding to that of the leading section and having corresponding base, top, and sidewalls;

a trailing shield section having a base, top, and sidewalls corresponding to the respective base, top, and sidewalls of the leading and intermediate sections;

excavation apparatus operatively disposed within the shield and including a mounting assembly secured to one of the walls of the shield;

boom means'pivotally mounted on the mounting assembly;

means for swiveling the boom means and for tilting the boom means, the boom means including an arm with a cutting blade thereon;

means for movement of the arm relative to the boom means;

a conveyor assembly for excavated material including an elongated conveyor frame having a first end positioned to receive material from the inclined plate and a second discharge end;

a conveyor in said frame to convey material deposited thereon from the plate;

planks are forced against the sidewalls of the trailing shield section.

4. The invention ofclaim 3, and:

shield advance means comprising a series of spaced apart hydraulic cylinder assemblies, each including a fixed housing secured to one of the walls of the intermediate shield section and extensible rod members engageable against the planks where extension of the rods forces the shield forwardly. 

1. Apparatus in a system for the excavation and lining of subterranean tunnels, comprising: I. A substantially rectangular shield having: a leading section with a base wall, sidewalls and a top wall; the top wall having a leading edge projecting forwardly and the base wall having a leading edge; the sidewalls having inclined leading edges connecting the leading edges of the top and base walls; an inclined plate mounted above the base wall and having a series of cutting teeth projecting forwardly of the leading edge thereof; the plate having an elevated discharge end extending inwardly and having side shield members vertically secured thereto; an intermediate shield section having base, top, and sidewalls common with the leading section, and having a structural member extending thereabout; the plate extending into the intermediate shield section; the base, top and sidewalls of the intermediate section terminating at interior, inwardly directed flanges; a trailing shield section having top, base and sidewalls coplanar with the respective top, base and sidewalls of the leading and intermediate shield sections; the sidewalls of the trailing shield section having flanges thereon which abut and are fixed to the flanges of the intermediate section; II. Excavation apparatus comprising: a mounting plate secured to the top wall of the intermediate section; a swivel member connected to the mounting plate for limited rotary movement; a generally vertical boom assembly depending from said swivel member and movable therewith; first extensible and retractable hydraulic cylinder means connected to the flange of the top wall of the intermediate shield section and to the boom assembly; second extensible and retractable hydraulic cylinder means incorporated in the boom assembly for imparting from front to rear tilt in the assembly about its pivot on the swivel plate; an arm connected to the boom assembly for vertical pivotal movement, the arm having a cutting blade on its distal end; third extensible and retractable hydraulic cylinder means mounted between the arm and the boom assembly, whereby the plate is extendable in a cutting stroke forwardly to at least the leading edge of the top, base and sidewalls of the leading shield sections; III. A conveyor for excavated material comprising: an elongated conveyor frame having a first end located below said elevated discharge end of the inclined plate; the frame having a second elevated end trailing the shield; support means for the frame; and an endless, chain-driven conveyor in the frame to convey material disposed thereon from the plate to a remote discharge location; IV. A liner plank installation means comprising: a pair of brackets secured in vertical position on the flanges of the sidewalls of the trailing shield section, each bracket having an upper end and a lower end; each bracket having a vertically extending slot formed in its upper end and having an attachment adjacent its lower end; a hydraulic cylinder for each bracket having a stationary portion connected to said attachment and having an extensible rod portion with an exterior clevis thereon; an elongated support arm in each of said clevises, the support being perpendicularly related to the slide members on one end and having flattop surfaces; the slide members being slidably disposed in the brackets with the support arms extending through said slots whereby a series of roofing planks placed on the top surfaces are elevated to a position adjacent to the top wall of the trailing shield section; a lateral hydraulic cylinder portably mounted in the trailing shield section and extensible to a distance such that side planks are forced against the sidewall of the trailing shield section simultaneously; and V. Shield advance means comprising: a serIes of spaced apart hydraulic cylinder assemblies, each including a fixed housing secured to one of the walls of the intermediate shield section and extensible rod member extended through openings formed in the abutting flanges of the intermediate and trailing shield sections; and the rod members having outer end sections engageable against the planks whereby extension of the rod forces the shield forwardly.
 2. Apparatus in a system for the excavation and lining of subterranean tunnels, comprising: a polygonal shield including a leading section having base, side, and top walls, at least the base and top walls having leading edges; an inclined plate mounted above the base and having a remote discharge end; an intermediate shield section of polygonal form corresponding to that of the leading section and having corresponding base, top, and sidewalls; a trailing shield section having a base, top, and sidewalls corresponding to the respective base, top, and sidewalls of the leading and intermediate sections; excavation apparatus operatively disposed within the shield and including a mounting assembly secured to one of the walls of the shield; boom means pivotally mounted on the mounting assembly; means for swiveling the boom means and for tilting the boom means, the boom means including an arm with a cutting blade thereon; means for movement of the arm relative to the boom means; a conveyor assembly for excavated material including an elongated conveyor frame having a first end positioned to receive material from the inclined plate and a second discharge end; a conveyor in said frame to convey material deposited thereon from the plate; liner plank installation means comprising plank elevator means, including power-actuated support arms, in the trailing shield section; support arms having upper surfaces to receive roofing planks whereby upon elevation of the support arms, the roofing planks are elevated; and means for the installation of side planks.
 3. The invention of claim 2 wherein: said means for installation of the side planks comprises portably mounted expansible cylinder means in the trailing shield section extensible to a distance such that side planks are forced against the sidewalls of the trailing shield section.
 4. The invention of claim 3, and: shield advance means comprising a series of spaced apart hydraulic cylinder assemblies, each including a fixed housing secured to one of the walls of the intermediate shield section and extensible rod members engageable against the planks where extension of the rods forces the shield forwardly. 